Small bowel displacement system-assisted intensity-modulated radiotherapy for cervical cancer

OBJECTIVE: To evaluate the small bowel displacement system (SBDS)-assisted intensity-modulated radiation therapy (IMRT) for cervical cancer patients. METHODS: Ten consecutive patients that received radiation therapy for uterine cervical cancer, with the SBDS, between January and May 2003, were included in this study. The SBDS consists of a customized Styrofoam compression device, which displaces the small bowel out of the radiation fields and an individualized immobilization abdominal board. Computed tomography (CT) scans were taken in the prone position, both with and without the SBDS. IMRT planning was performed for both CT sets using 15 MV photon beams. The dose distributions in the target volumes and the organs at risk, with and without the SBDS, were compared. The complexity of both the IMRT plans was evaluated by comparing the monitor units (MUs) and multi-leaf collimator (MLC) segment numbers of the plans. RESULTS: The SBDS significantly reduced the small bowel volume within the pelvic radiation field. The mean irradiated small bowel volume, with the SBDS, was 61.46 +/- 4.97% (53.4-97.1%) smaller than the conventional IMRT. The SBDS-assisted IMRT plan was superior to the conventional one in terms of the dose homogeneity in the planning target volume (PTV) but not significantly different in the rectum and bladder. The mean MUs and MLC segment numbers, with the SBDS, were 26.2% and 31.65% lower than the values without the SBDS, respectively (P < 0.0001 for MUs and MLCs). CONCLUSIONS: The SBDS-assisted IMRT is superior to conventional IMRT in terms of the dose homogeneity of PTV and in sparing of the small bowel, which potentially allows dose escalation by further reducing the small bowel complications.